The Invention is based on a mounting plate.
Wiper systems with multiple windshield wipers for motor vehicles are fastened with their wiper bearings directly or indirectly to the body of the motor vehicle via a mounting plate. The mounting plate, or a tubular mounting platexe2x80x94if the wiper carrier also includes tubular hollow profilesxe2x80x94includes a motor mounting plate, which carries a wiper drive with a wiper motor and a gear mounted on it. A power takeoff shaft of the gear is supported in a gear dome and, as a rule via a crank and connecting rods, drives further cranks that are solidly connected to a drive shaft for each windshield wiper.
It is also possible for only the drive shaft of a windshield wiper to be driven by the wiper motor, while another windshield wiper can be connected to the first windshield wiper via a four-bar lever mechanism and has a bearing shaft. The drive shaft or bearing shaft associated with one windshield wiper is supported in a wiper bearing. The remarks hereinafter regarding a drive shaft will logically apply to a bearing shaft as well, and this will no longer be expressly mentioned.
The bearing housings are fastened to the ends of the mounting plate or integrally molded on. The mounting plate positions the wiper drive relative to the wiper bearings and essentially absorbs the driving forces generated by the wiper drive. It also determines the positioning angle of the shafts of the wiper bearings relative to the vehicle window and thus the approximate position of the wiper blade. For a good outcome of wiping, its shape stability over its service life, under the influence of extreme operating parameters such as temperatures, blockage by a load of snow, vibration, jarring, and so forth, is therefore especially important. The mounting plate furthermore serves the purpose of premounting of the driving parts and wiper bearings, to make installation on the vehicle easier.
From German Utility Model DE-GM 74 34 119, a tubular mounting plate is known that is made from a square tube, to which a plate acting as a motor mounting plate is welded. A wiper bearing is fixed to each of the ends of the square tube. To that end, the housing of the wiper bearing has attachments, which are inserted into the mounting tube and secured by screws or wobble riveting. The attachment can also be slightly conical, and the mounting tube can be retained by a press fit. Such tubular mounting plates or tubular frame systems are quite stable despite their lightweight design, but numerous assembly operations are required, and the connection points must be monitored carefully. For reasons of cost, it is a goal to produce a straight carrier tube that does not require any prebending.
From European Patent Disclosure EP 06 889 75 A1, a tubular mounting plate with a motor mounting plate is also known. This tubular mounting plate comprises two mirror-symmetrical parts, which on the side toward a tubular mounting plate have indentations in which the tubular mounting plate is embedded. The indentations each surround the tubular mounting plate over a circumferential range of approximately 180xc2x0, so that both indentations together surround the tubular mounting plate over its complete circumference. Upon installation, both parts of the motor mounting plate are placed around the tubular mounting plate and joined together, for instance mechanically, by adhesive bonding or by means of a thermal connection. This fixes the tubular mounting plate relative to the motor mounting plate in the circumferential and axial directions by positive engagement and/or by material engagement by adhesive bonding. The two parts of the motor mounting plate can be made from plastic or metal, and in one feature can also be combined into one piece.
Mounting tubes assembled from many components have numerous interfaces, whose individual tolerances add up to a total tolerance. To achieve adequate quality, close individual tolerances must be prescribed, which makes the production cost higher. Deviations from an optimal angular location and position of the wiper bearings relative to the wiper motor and/or the vehicle window can increase the driving forces and worsen the outcome of wiping. Furthermore, the numerous assembly steps increase installation costs.
Die-cast tubular mounting plates are also known, which have a load-bearing cast body with a honeycomblike reinforcing structuring. Openings for receiving a wiper drive and the wiper bearings as well as fastening points for installation in a vehicle are as a rule integrated. While the bearing points are integrally formed on and for the most part are cast in final form, the decoupling elements have to be installed separately. Compared with sheet metal, the material is expensive, and it has less strength, especially with regard to dynamic stresses.
Mounting tubes of plastic have a small number of components. The bearing points can be integrally formed in the course of production and partly injection molded in complete form. The material, however, in general has low strength and in particular inadequate shape stability, so that the settings can vary sharply under load. Furthermore, plastics have an unfavorable aging and temperature behavior. They shrink, swell, and become brittle over the course of time, and their strength properties change, especially under extreme ambient conditions. To achieve greater strength of the mounting plate, the plastic must be reinforced with fibrous materials, such as glass fibers or carbon fibers. Fiber-reinforced plastics are expensive to produce, since they require special production methods. In addition, at low temperatures they have a tendency to brittle fracture.
According to the invention, the mounting plate comprises at least two components, and one half-shell-like bent sheet-metal part is connected by injection molding to a plastic body that braces the bent sheet-metal part on the inside. A receptacle for a wiper drive and bearing points for wiper bearings as well as fastening points for installation in a vehicle are expediently integrated, so that they can all be produced in the same production process. As a result, low tolerances with regard to the position and angular location can be adhered to.
The bent sheet-metal part, because it is in the form of a half shell, assures durable shape stability and strength, even under extremely high dynamic bending stress, and the plastic body together with the bent sheet-metal part assures good torsional strength. Even during the injection molding of the plastic body, the bent sheet-metal part largely prevents shrinkage and vanishing of the plastic material upon cooling down, so that high precision with regard to the bearing spacings and the axial angles are attained. Since the bent sheet-metal part does not age or swell, the dimensions and strength values are preserved over the service life. By means of the mounting plate, the positioning angle of the bearing shafts relative to the vehicle window is defined. High shape stability of the mounting plate therefore assures a precise setting of the angular locations and assures a wiper outcome that remains constantly good.
The connection of a thin-walled bent sheet-metal part with plastic is of lightweight construction and nevertheless has bending strength and torsional strength, so that the mounting plate has low weight. As a rule, plastic that is not fiber-reinforced suffices for the plastic body, but plastic that is reinforced with glass fibers or carbon fibers can also be employed. Non-fiber-reinforced plastic has the advantage that it is easier to process, remains relatively elastic at low temperatures, and does not have a tendency to brittle fracture. The plastic body itself can be embodied in lightweight form by being provided with ribs in some parts or embodying it as a hollow profile. The tall cross section, while using little material and being low in weight, assures good torsional strength of the mounting plate. Beads in the bent sheet-metal part can also be omitted, since the bent sheet-metal part already has good bending strength because of its being reshaped into a U-shaped, half-shell-shaped profile. The plastic body is expediently disposed predominantly on the side of the mounting plate that is subjected to pressure in the control situation, while the bent sheet-metal part with a markedly greater tensile strength is located predominantly in the region of the tensile forces. Since the high tensile strength of the bent sheet-metal part is combined with the low weight of the plastic body, overall a small structural volume and low weight are achieved along with high shape stability.
As a result of the injection molding process, the plastic body adheres by material engagement to the bent sheet-metal part. To reinforce the connection between the components and make it more durable, positive-engagement elements, perforations in the bent sheet-metal part, or eyelets of the bent sheet-metal part made into the plastic body, are expediently provided between components. The holes can be utilized during the injection molding as injection conduits for the plastic.
The plastic body can furthermore contribute to corrosion protection, especially if it covers the bent sheet-metal part over a large area from both sides or embeds it entirely. For corrosion protection, the bent sheet-metal part is also expediently made of zinc-coated steel, or aluminum or an aluminum alloy. The plastic body prevents possible contact corrosion at the fastening points.
For integrating a wiper bearing and/or a receptacle for the wiper drive and/or a fastening point, the bent sheet-metal part in the region has breaches, which are adjoined by cylindrical stubs that are expediently integrally molded on. In the injection molding of the plastic body, these stubs are extrusion coated in such a way that finished bearing points are created, which protrude past the stubs at the top and bottom. The plastic of the plastic body simultaneously serves as the bearing material. Required lubrication grooves can also be incorporated. Thus given a suitable choice of the plastic, the installation of additional bearing bushes and postmachining of the bearing points can be omitted. Good sliding and wear properties of the plastic at the same time enhance the service life and improve the noise performance.
In the same vise as the one used for the plastic extrusion coating, a second, elastic material component, with which the decoupling elements are formed, can be injected afterward or, given a suitable embodiment of the material, simultaneously. This further reduces the number of individual parts, and assembly steps otherwise required are omitted. Sources of mistakes from incorrect assembly are likewise precluded.